A large output power is required for a drive motor used in an electric vehicle and a hybrid vehicle (a drive rotary electric machine). Therefore, there is generally used a permanent magnet-type motor which uses a sintered magnet containing a rare earth element to hold a strong energy. As a drive motor, an embedded magnet motor which satisfies requirements such as a large torque at a low speed and a wide rotation speed range is used among the permanent magnet-type motors.
By the way, torque ripples of the motor cause noises and vibrations. In particular, the torque ripples generated at a low speed in the electric vehicle causes uncomfortable to ride in. In a conventional permanent magnet-type motor, skewing is performed as a countermeasure in order to reduce the torque ripples.
For example, PTL 1 discloses a motor in which grooves are provided in a magnetic steel plate on the peripheral sides of the embedded magnet, and disposed to be deviated in an axial direction.